The present invention relates to a hermetic compressor and parts thereof, and more particularly to such a compressor for refrigerators.
In a reciprocating refrigerant compressor for cooling systems, such as a refrigerator or freezer, it is very desirable to improve compression efficiency. When the refrigerant gas recycled from the cooling system is expanded by heat within the compressor, the resultant reduced density gas must then be re-compressed by the compression cylinder, thereby decreasing the compression efficiency. One way to improve compression efficiency is to prevent the decrease of density within the compressor of the refrigerant gas recycled from the cooling system.
A specific example of such a system is disclosed in U.S. Pat. No. 4,531,894, wherein the refrigerant gas from the cooling system is guided directly to a suction muffler made of a synthetic resin of low thermal conductivity within the compressor, with the suction muffler being connected to a suction plenum communicating therewith via a metallic pipe. Another example, U.S. Pat. No. 4,401,418, discloses a compressor wherein the inlet of a suction muffler made of a synthetic resin of low thermal conductivity is formed in the shape of a horn for blowing of the suction gas, with the suction muffler being in communication with the suction plenum via a metallic pipe. In compressors of such types, however, because the metallic pipe has a high thermal conductivity and the cylinder head defining the suction plenum is made of a material of high thermal conductivity, such as cast iron or aluminum alloy, the suction gas is subject to substantial heating by the pipe and cylinder head.
In order to further reduce the effect of heat on the suction gas, European Patent No. 195486A2 and U.S. Pat. No. 4,784,581 propose compressors wherein a metal discharge chamber and a synthetic resin suction chamber are separately assembled to the valve plate of the cylinder block to minimize heat conduction therebetween. The flow passage or communicating duct (from the synthetic resin suction muffler to the synthetic resin suction plenum) is formed of synthetic resin and integral with the suction muffler, with the suction chamber or plenum being disposed at the leading end of the flow passage. However, in these systems, the suction chamber (at the leading end of the suction muffler) and the discharge chamber must be independently mounted and sealingly held in contact with their respective ports adjacent the cylinder head. In addition, if the contact between the suction port and the suction chamber is not completely airtight, suction noise is produced. Therefore, care must be exercised in ensuring a hermetic seal between the suction port and the suction chamber. Thus the cost of manufacture and assembly is relatively expensive.
Accordingly, it is an object of the present invention to provide a hermetic compressor of improved compression efficiency.
Another object is to provide such a compressor wherein an integral unitary metallic cylinder head defines both the suction chamber and the discharge chamber, but with minimal heating of suction gas in the suction chamber by the hotter gas in the discharge chamber.
A further object is to provide such a compressor wherein the suction muffler and cylinder head may be preassembled at the factory to minimize on site assembly work.
It is also an object to provide such a compressor wherein suction noise is minimized.
It is another object to provide such a compressor wherein the suction muffler is held against rotation relative to the cylinder head.